Apply armature's object rotation to animation data
The answer lies in the MakeHuman Blender tools. There are a few steps you need to get right, though:


Load a BVH with the "Load BVH" button in the "Misc" tab. This will cause the BVH to be loaded incorrectly, as it'll be scaled down. Unfortunately you can only change this behaviour after you loaded the BVH. We'll fix this, and then re-load the BVH correctly.
Open the "MakeWalk: Options" panel.
Deselect the "Auto Scale" checkbox and/or set the scale to 1.00.
Scroll down to the "MakeWalk: Utilities" panel and click "Save defaults".
Remove the armature from the scene, and load your BVH again.
Open "MakeWalk: Edit Actions" and enable "Global Edit".


Now you can go to Pose Mode, move the armature around, and click on the "Shift Animation" button. Contrary to its name, this also applies rotations. It then applies your translation &amp; rotation to the entire animation.